Guns

Goulet

Thiry guns per ton of butter,
or equivalently gun of 1/30 ton of butter per gun.
Note that at this price,
you would find the price of butter (30 guns/ton)
greater then his marginal cost of producing butter (20 guns/ton),
and thus
be induced to specialize in the production of butter
and trade some of your butter for guns.

sevensins

i put butter on toast